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    <title>Document</title>
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<body>
    <script>
        var arr=[21,12,1,3,4]

        var c=arr.sort((a,b)=>{
            return a-b;
        })
        console.log(c)   //[1,3,4,12,21]


        /* 利用算法的方法升序 */
        /* for(let i=0;i<arr.length;i++){
            for(let i=0;i<arr.length;i++){
                if(arr[i]>arr[i+1]){
                var temp=arr[i];
                arr[i]=arr[i+1];
                arr[i+1]=temp;
                }
            }
        }
        console.log(arr) */
    </script>
</body>
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